1. Field of the Invention
The present invention relates to a process for upgrading a liquid petroleum or chemical stream wherein said feedstream flows countercurrent to the flow of a treat gas, such as a hydrogen-containing gas, in at least one reaction zone. The feedstream treated so that it is substantially free of particulate matter and foulant precursors.
2. Background of the Invention
There is a continuing need in the petroleum refining and chemical industries for catalyst and process technology that result in increase yields of desirable products and lower yields of undesirable components, especially those related to environmental concerns. One such process technology, hydroprocessing, has been subjected to increasing demands for improved heteroatom removal, aromatic saturation, and boiling point reduction. More active catalysts and improved reaction vessel designs are needed to meet these demands. Countercurrent hydroprocessing, where the liquid feedstream flows counter to upflowing treat gas, has the potential of meeting some of these demands because they offer certain advantages over co-current process where the liquid feedstream and treat gas flow co-currently. Countercurrent hydroprocessing is well known, but it has never reached its commercial potential, primarily because of flooding problems.
A particulate containing feed, which would not cause noticeable fouling or operating difficulties when processed in a cocurrent flow reactor, was discovered to cause significant fouling of a countercurrent flow reactor. This fouling will cause the countercurrent flow reactor to be inoperable due to flooding. It is suspected that reactive species (i.e., dienes, peroxides, etc.) that could form polymeric material are the cause for fouling in a countercurrent reactor. Thus, it is highly desirable that particulates be removed from feedstreams that are to be processed in such reactors. The prior art does not address fouling and how to mitigate it when it happens. Therefore, there still exists a need for improved countercurrent hydroprocessing reactor designs.
In accordance with the present invention there is provided a process for hydroprocessing a hydrocarbonaceous feedstream, which process comprises:
a) treating said feedstream to remove particulates and/or foulant precursors;
b) introducing said treated feedstream into a reaction vessel upstream from at least one reaction zone and passing said feedstream through one or more reaction zones operated at hydroprocessing conditions, wherein each reaction zone contains a bed of hydroprocessing catalyst;
c) introducing a hydrogen-containing treat gas at the bottom of said reaction vessel and passing it upward through at least one reaction zone countercurrent to the flow of liquid feedstream, thereby reacting with said feedstream in the presence of said hydroprocessing catalysts and resulting in a liquid phase product stream and a vapor phase product stream;
d) passing the liquid phase product out of the bottom of said reaction vessels; and
e) removing the vapor phase product stream overhead of said reaction zones.
In a preferred embodiment of the present invention said treating is done in contact with a hydrogen-containing treat gas in a reaction zone containing a catalyst which is effective for converting said foulant precursors to non foulant components.
In another preferred embodiment of the present invention the physical aspects of the catalyst are such that the catalyst bed physically filters the largest 10% of the particles present in the feedstream.
In yet another preferred embodiment of the present invention the filtration is achieved by a mechanical filtration means to remove the largest 10% of the particles.